Stop overscroll UITableView only at the top?

For Swift 2.2, Use

func scrollViewDidScroll(scrollView: UIScrollView) {
    if scrollView == self.tableView {
        if scrollView.contentOffset.y <= 0 {
            scrollView.contentOffset = CGPoint.zero
        }
    }
}

For Objective C

    -(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    if (scrollView.contentOffset.y<=0) {
        scrollView.contentOffset = CGPointZero;
    }
}

You can achieve it by changing the bounce property in scrollViewDidScroll of the tableView (you need to be the delegate of the tableView)

Have a property for the lastY:

var lastY: CGFloat = 0.0

Set initial bounce to false in viewDidLoad:

tableView.bounces = false

and:

func scrollViewDidScroll(scrollView: UIScrollView) {
    let currentY = scrollView.contentOffset.y
    let currentBottomY = scrollView.frame.size.height + currentY
    if currentY > lastY {
        //"scrolling down"
        tableView.bounces = true
    } else {
        //"scrolling up"
        // Check that we are not in bottom bounce
        if currentBottomY < scrollView.contentSize.height + scrollView.contentInset.bottom {
            tableView.bounces = false
        }
    }
    lastY = scrollView.contentOffset.y
}